For someone to be guitly of a CRIME there must be intent to commit the crime. Texas' law is from an archaic time before much was understood about mental illness and has not been updated. If she killed because she believed she was saving them from damnation, and that belief was a result of an illness for which, with proper medication, whe would not be possesed of that idea, well, if you wish to kill her for that, in my opinion, your philosphy lacks an important eliment in civil society, humanity.
All the best, Larry
PS I don't think that anyone who kills there kids are psycotic... perhaps sociopathic, for example the father who killed his kid for insurance... that is different than being phsycotic for want of proper medication.